Vietnam Academy of Science and Technology: Journals Online
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Partial purification and characterization of a superoxide distimutase (SOD1) from black tiger shrimps Penaeus monodon
Full text linkSuperroxide dismutase (SOD, EC.1.15.1.1) is the enzyme which dismutates superoxide radicals and plays an important role in protection of living cells against oxidative stress. SOD is also involved in immune response in shrimps. In this study, it was found that the total SOD activity of black tiger shrimp muscular tissues is 10 fold higher than that of the haemolymph, however, the specific activity of SOD in the shrimp haemolymph is 9.2 fold higher than that of muscular tissues. By using active gel electrophoresis, 2 different SOD forms were found in black tiger shrimps (one in muscular tissues and two in haemolymph).Using DE-52 cellulose and Q-Sepharose ion exchange column chromatography, one SOD (SOD1) from black tiger shrimp haemolymph was partially purified, and its purity was 31.2 times higher than that of the starting haemolymph. The SOD1 was shown to have mainly one protein band of approximately 24 kDa on SDS-PAGE. SOD1 was most active at 45oC and pH of 5.5. At a concentration of 5 mM, Mn2+ strongly activated SOD1 (up 200% activity), Ca2+ và Zn2+ could increase approximately 20% activity while Cu2+ inhibited more than 60% ativity of the enzyme.
COMPUTATION FOR THE DELAMINATION IN THE LAMINATE COMPOSITE MATERIAL USING A COHESIVE ZONE MODEL BY ABAQUS
Full text linkIn this paper, a damage model using cohesive damage zone for the simulation of progressive delamination under variable mode is presented. The constitutive relations, based on liner softening law, are using for formulation of the delamination onset and propagation. The implementation of the cohesive elements is described, along with instructions on how to incorporate the elements into a finite element mesh. The model is implemented in a finite element formulation in ABAQUS. The numerical results given by the model are compare with experimental dat
STUDYING ON FAILURE MECHANISM OF 2D GRANULAR COLUMNS: NUMERICAL RESULTS
No full textThe failure mechanism of granular columns and the characteristics of this failure flows have been intersted in researching in recent years. In particular, the experiments in failure mechanism and failure flow of 2D granular column are not often 2D standard. Therefore, Cuong T. Nguyen et al. (2015) conducted research this problem based on 2D standard in the laboratory and developed a numerical computation model using SPH (Smooth Particles Hydrodynamics) method (Cuong T. Nguyen et al., 2017). This model has proven the reliability by verification of calculation and experimental results. In this paper, the developed numerical model is used to perform a series of numerical experiments that some are difficult or impossible to obtain accurate results by physical experiment model to re-examine the previously identified characteristics and find out the rules more general of this failure flow
CREEP ANALYSIS OF CONCRETE COLUMNS BY USING FINITE ELEMENT METHOD
No full textThe authors have carried out studies on long term behavior of concrete-filled steel tubular (CFST) column by numerical methods based on experimental data that is described by a visco-elastic model, and the age-adjusted effective modulus (AAEM) method is adopted to modeling creep behavior of the concrete core, which is evaluated by the Finite Element Method (FEM) combined Prony's series interpolation by using ANSYS software. The CFST column with circular sections under long term sustained loading are performed, ensure the ultimate load bearing capacity of the members is limited to cause cracks. In the material modeling, the confining effect of the concrete was taken into account while the steel was modeled as a bilinear kinematic hardening model with perfect bond between concrete and steel. The scope of applicability, advantages over other methods and limitations are discussed in detail
Effect of Polypyrrole on the Electrical, Dielectric and Mechanical Properties of Waterborne Epoxy Coatings
Full text linkIn this context, conducting composite based on waterborne epoxy system and polypyrrole (PPy) was investigated. The polypyrrole was synthesized by chemical oxidation polymerization. Its morphology and chemical structure were confirmed by using field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). Then, PPy was well-dispersed in the epoxy coating and had a good compatibility with the matrix. The effects of PPy on dielectric, electrical and mechanical properties of epoxy/PPy composites was examined. The dielectric constant and electrical conductivity of the coatings increased with addition of PPy fillers. Over to 15 wt. % of PPy loading, the volume resistivity of samples slightly decreased from 6.7 × 1010 to 1.5 × 1010 Ω cm. In contrast, the presence of PPy diminished both impact and abrasion resistance of the epoxy/PPy composites, down to 160 kg cm and 10.2 L/mil, respectively, but they stayed acceptable for the coatings. The results reveal that the epoxy containing polypyrrole is suitable for various electrical and dielectric applications
The status of southern white-cheeked gibbon (Nomascus siki) in Truong Son key biodiversity area
Full text linkThe Southern white-cheeked crested gibbon, Nomascus siki, is an endemic primate to Vietnam and Laos, and has been identified as a nationally and globally endangered species (EN). However, little information is known on the status of the species in Vietnam generally and in the Truong Son key biodiversity area (Truong Son KBA) particularly. In order to explore the current status of the species in the Truong Son KBA, we conducted field surveys in 2018 and 2019. Analysis of the survey data shows 149 groups of gibbon in the 4 study areas. Combined with results of similar-techniqued survey in 2016 on the same species in Khe Nuoc Trong forest, we identified at least 252 gibbon groups and estimated 425 gibbon groups in the entire Truong Son KBA. These gibbon groups are mainly distributed in medium-rich evergreen closed forests in mountainous areas of the west Truong Son KBA, adjacent to the Vietnam-Laos border.
Estimation of heat transfer parameters by using trained POD-RBF and Grey Wolf Optimizer
No full textThe article presents a numerical model for estimation of heat transfer parameters, e.g. thermal conductivity and convective coefficient, in two-dimensional solid bodies under steady-state conduction. This inverse problem is stated as an optimization problem, in which input is reference temperature data and the output is the design variables, i.e. the thermal properties to be identified. The search for optimum design variables is conducted by using a recent heuristic method, namely Grey Wolf Optimizer. During the heuristic search, direct heat conduction problem has to be solved several times. The set of heat transfer parameters that lead to smallest error rate between computed temperature field and reference one is the optimum output of the inverse problem. In order to accelerate the process, the model order reduction technique Proper-Orthogonal-Decomposition (POD) is used. The idea is to express the direct solution (temperature field) as a linear combination of orthogonal basis vectors. Practically, a majority of the basis vectors can be truncated, without losing much accuracy. The amplitude of this reduced-order approximation is then further interpolated by Radial Basis Functions (RBF). The whole scheme, named as trained POD-RBF, is then used as a surrogate model to retrieve the heat transfer parameters
The process for the production of high phospholipid containing eicosanoids and soluble oligopeptides from the Oyster. sp.
No full textOysters could be found in seashore and estuarine areas and is regarded as a valuable export product with high economic value. In addition, the oysters could serve as an efficient assimilator of nutrients and potential source of polyunsaturated fatty acids (PUFA), mainly omega-3 fatty acids, which have been found to be responsible for a wide array of health benefits. In this paper, we report a process for the production of high phospholipid containing eicosanoids and soluble oligopeptides from the Oyster. sp. This result shows phospholipid layer containing high eicosanoids with 34.4% and soluble oligopeptides containing 8 essential acid amides. 19.53 g histidine per 100 g oligopeptides pointed out that hydrolyzed oysters are highly nutritional and valuable pharmacological products
Some features of marine dynamics caused by damrey typhoon (11/2017) and its impacts on coral reef in Ninh Van waters, Khanh Hoa province
Full text linkTyphoon Damrey (Vietnamese name is Typhoon No.12 in 2017) landed in South Phu Yen - North Khanh Hoa provinces in the morning of 4th Nov 2017 causing severe damage to people, material and serious consequences on the social and economy of the region (especially Khanh Hoa Province). So far, there have been no published papers and reports on the results of analysis of observing and monitoring data, calculations on marine dynamics as well as their impact on some marine ecosystems. Based on the results of coral reef survey in the study area before and after storm as well as hydrodynamic model results, the paper presents some results of data analysis of monitoring water level, calculations of wave field, currents caused by Damrey Typhoon in coastal waters of Khanh Hoa Province. On that basis, there have initial comments on the impact of storm on the coral reef of this region for management, forecasting and mitigation of local natural disaster damage in the future
Mechanism of Inverse Magnetoresistance in High- Annealed MnNi/Co/Ag(Cu)/Py Spin Valves
Full text linkThe magnetic transport properties -- magnetoresistive (MR) effects of MnNi/Co/Ag(Cu)/\break Py pinned spin valve structures (SVs) prepared by rf sputtering method and annealed at °C - 500°C for 30 minutes in high vacuum ( torr) are investigated. The received results show a change in the observed MR behaviors from a normal giant magnetoresistance effect to an inverse magnetoresistance effect after annealing at high temperatures, 300°C and 400°C, for these SVs. The origin and mechanism of the IMR behavior are analyzed and discussed. These results will suggest an ability to manufacture SV devices used the IMR effect for enhancing the application capacities for SV-sensor systems